A relay, also known in some countries What relay or relay, it’s a switch whose control is carried out by an electric circuit. Developed in the first half of XIX century by the American physicist Joseph henry, through a coil and a electromagnet it affects various contacts to open or close other circuits, which work independently.
What does the coil is to create a magnetic field that leads the contacts to establish a connection. The electromagnet, for its part, allows the closure of the contacts. In this way, the relay acts as a switch that can promote the passage of electrical current or its interruption.
The relays, in short, allow to develop a remote commutation, controlling high voltages with a low return voltage. They also serve to interrupt the alternating current supply. The automobiles and the telephonic centralFor example, they have relays.
In simpler words, the relay allows to control a large number of electricity operating with a very small amount. These are instruments that provide greater safety in different devices that work with the use of electrical energy, since their contacts allow to open or close electrical circuits (that is, to generate or interrupt the connection).
According to the delay in deactivation and activation, the intensity that they tolerate and the number of contacts, it is possible to classify the relays in different ways, as can be seen below.
This, in turn, is divided into several types:
* armor type: It is the oldest, but this does not mean that it is also the most used in a large number of applications. It consists of an electromagnet which, when excited, generates the tilting of an armature, through the closing or opening of the contacts as required. normally closed (NC) or normally open (NA);
* moving core: where the previous one has an armature, this one has a plunger. Since it has a greater attractive force, it becomes necessary to use a physical device known as solenoid to close the contacts. The solenoid can generate a countryside extremely intense and highly uniform magnetic inside, and with low intensity outside;
* reed: also known as reed, and consists of a glass bulb that has within it a series of contacts arranged on top of thin metal sheets.
Solid state relay
It’s about a circuit hybrid that usually consists of a device such as the triac, which serves to interrupt the power, a trip circuit, which is responsible for detecting the passage of the line current through zero, and a optocoupler, for input isolation.
The origin of its name is that it resembles an electromechanical one and its most common applications involve the constant use of contacts that would wear a conventional relay too much, and the switching of high amperes that could destroy the contacts of an electromechanical relay in a very short time.
Alternating current relay
By energizing the coil of a relay with alternating current, the magnetic flux also alternates and this produces a force on the double and pulsating type contacts. frequency. In some parts of the world, such as Latin America and certain European countries, the contacts of a relay connected to a network oscillate at 2 x 50 Hz, while in North America they do so at 2 x 60 Hz (something that is used as a basis for buzzers and buzzers); An alternating current relay has the mission of modifying the resonance to avoid said oscillation.